Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the workpiece. Soldering differs from welding in that soldering does not involve melting the work pieces. In brazing, the filler metal melts at a higher temperature, but the workpiece metal does not melt. Formerly nearly all solders contained lead, but environmental concerns have increasingly dictated use of lead-free alloys for electronics and plumbing purposes.

There is evidence that soldering was employed up to 5000 years ago in Mesopotamia. Soldering and brazing are thought to have arisen very early in the history of metal-working, probably before 4000 BCE [2]. Sumerian swords from ~3000 BCE were assembled using hard soldering.

Soldering was historically used to make jewelry items, cooking ware and tools, as well as other uses such as in assembling stained glass.

Soldering is used in plumbing, in electronics and metalwork from flashing to jewelry.